In a charging circuit of an electric vehicle, a relay circuit for connecting and disconnecting a quick charger to and from a junction circuit for connecting a storage battery during charging has been used heretofore. Such a relay circuit includes mechanical relay contacts (hereinafter, referred to as “relay”) used therein, and such a relay is sometimes welded due to an on-off operation during application of a high voltage and high current. Relay welding detection circuits for detecting this kind of welding of a relay are known (e.g., see Patent Literature (hereinafter, referred to as “PTL”) 1).
In PTL 1, a dead front relay (DFR) is provided between a charging inlet and a neutral point of a motor, and in addition, a voltage sensor is provided between the charging inlet and DFR. In PTL 1, one DFR is turned on while the other DFR is turned off, and when the voltage sensor detects a voltage, it is determined that the DFR that has been turned off is welded.
Moreover, detection of electrical leakage on a vehicle side using a charger has been known, heretofore (PTL 2).